1. Field of the Invention
The present invention relates generally to workpiece contour inspection and, more particularly, is concerned with an apparatus and method for automated inspection of a surface contour on a workpiece, such as a circumferential groove on a roller die of a cold-pilgering machine use in fabricating nuclear fuel rod tubes.
2. Description of the Prior Art
Cold-pilgering is a conventional process by which a tube is advanced over a stationary mandrel and simultaneously compressed using two opposing roller dies resulting in the reduction of the cross-sectional area and in elongation of the tube. Reduction is effected in both the diameter and wall thickness of the tube by means of the tapered shape of the mandrel and the circumferential tapered profile of grooves in the roller dies which embrace the tube from above and below the mandrel and roll in a constant cycle back and forth along the tube.
Each roller die is manufactured using a conventional hot isostatic pressing process. The grooves are machined to their final contoured profile using a conventional electric discharge machining method and/or diamond wheel grinding technique followed by a polishing operation. Then, to ensure that the tubes will be fabricated with their wall thicknesses and diameters meeting precise specifications, the groove contour of the newly-fabricated roller dies are inspected prior to use. Also, used roller dies are inspected after certain periods of use.
Heretofore, these inspections have been performed by trained operators manually making groove contour measurements. As a result, the reliability of die inspections are subject to variances caused by the different degrees of care taken by different operators and also their different levels of skill. Consequently, a need exists for an improved technique for reducing or eliminating operator involvement in the inspection process.